... <brainwave/> I've been thinking of each note as a single Metropolis sampler step, and adding a cludgy thing to make it consider multiple note destinations per step. I now think I may be better off considering notes as regularly subsampled from a completely normal Metropolis sampler. Here's the neat bit: Previously it never repeated the same note (midi above has a cludge to add repeats, but it's a bit too uniform). Note hits only occurred when the note changed. But with the subsampling method, I can say "repeat the note whenever there is a change, even if it changes back before the next note". This is neat because "unstable" notes, notes with close neighbours of comparable likelihood, get lots of repeats.